Method of impregnating fibrous materials



United States Patent METHOD OF IMPREGNATING FIBROUS MATERIALS Henry C. Crandall, Mosinee, Wis., assignor to Mosinee Paper Mills Company, a corporation of Wisconsin No Drawing. Application June 24, 1952, Serial No. '295t364 2 Claims. (Cl. 92-6) My invention relates to a method of impregnating fibrous materials and the products resulting therefrom, and more particularly, to a method of preparing moldproof paper and to the moldproof paper obtained by carrying out the instant method.

In the paper making art, the incorporation of active fungicides in paper so as to obtain a moldproof paper has presented numerous problems. Heretofore, the treatment of papers with a water-soluble fungicide such as sodium pentachlorophenate has been carried out in a conventional size press, but the fungicidal character of the paper was quickly lost on exposure to water or moist conditions.

In accordance with my invention, however, an insoluble fungicide is applied to the paper fibers by being intimately dispersed in the beater in small amounts. Because of the high cost of the insoluble fungicides which I use, it would be expected that the use of such materials would not be practical in the paper making art, and in particular, it would be expected that such materials could not be used in the beater. My invention provides for a method for obtaining unusally good retention of these materials on the fibers and subsequently on the formed de-watered paper web, so that inexpensive paper having unique fungicidal properties may be obtained.

As hereinbefore mentioned, I first effect an intimate dispersion in the beater of an insoluble fungicide. I may accomplish this merely by mechanical processes, but preferably I render the fungicide insoluble in the stock, in situ, while it is intimately dispersed therein. This may be done by breaking or coagulating a suspension of the material in the stock, or by causing the formation of the material in the stock by reaction of two intimately dispersed or dissolved ingredients in the stock. Also, I have discovered that greatly improved fungicide retention in the paper product is obtained if rosin size is added at the beater and/or if a substantive agent is added during the dispersion of the fungicide.

It is, therefore, an important object of my invention to provide an improved method for preparing moldproof paper, and an improved moldproof paper resulting from carrying out such method.

As used herein, the notation 0.01-5 means from 0.01% to 5%.

It is another object of my invention to provide a method of preparing moldproof paper that comprises the step of intimately dispersing in paper stock in the paper machine beater 0.01-5 dry fiber weight percent of an insoluble fungicide and 0.015 dry fiber weight percent of substantive agent.

It is still a further object of my invention to provide an improved method of preparing moldproof paper that comprises the step of intimately dispersing in paper stock in the paper machine beater 0.01-5 dry fiber weight percent of an insoluble fungicide, 0.01-5 dry fiber weight percent of a substantive agent, and 0.01-5 dry fiber weightpercent of rosin size.

Other objects, features, and advantages of my invention will become apparent to those skilled in the art from the following detailed description of preferred embodiments of my invention.

My invention consists in a method of preparingmoldproof paper that comprises the step of intimately dis- 2,767,088 Patented Oct. 16, 1956 persing in paper stock in the paper machine beater 0.01-5 dry fiber weight percent of an insoluble fungicide and 001-5 dry fiber weight percent of rosin size and a substantive agent.

As suitable insoluble fungicides, I may use the following:

(l) Copper pentachlorophenate, which may be obtained by precipitation of sodium pentachlorophenate with copper sulfate. Precipitation may be accomplished either in the beater with the stock or outside the beater in a preliminary operation followed by addition of the copper pentachlorophenate as a dispersion in water, for example.

In general, I have found that these insoluble fungicides may be dispersed in the stock in the beater in minute proportions of about 0.01-5 dry fiber weight percent. The dry fiber weight content of stock in the beater is usually about 3.5 plus or minus 0.5% of the stock, the remainder being water, so the amount of fungicide employed in the stock is very small and there is a very substantial quantity of water in which it is dispersed. Larger amounts of fungicide may, of course, be used, but there is no necessity for the use of larger amounts, and the use of substantially larger amounts may be quite wasteful. Even though the fungicides employed are insoluble, they are employed in such small quantities in the great volume of water in the stock, that the fungicide particles do not tend to settle out to an appreciable extent, if used in the minute proportions herein mentioned. Also, the presence of fibers in the stock tends to hold the insoluble particles up in suspension in the aqueous stock system.

In fact, it is believed that the unique advantageous features of the instant invention are attributable to a substantial extent to the fact that the suspended fibers in the stock tend to attract and retain the insoluble fungicide particles in such a manner that, after additional treatments including the addition of rosin and/or substantive agents, web formation, de-watering of the web and pressing of the web, an unusually good retention of the fungicides in the web is obtained.

As hereinbefore indicated, the insoluble fungicide employed is preferably formed, in situ, in the beater. By such a procedure the most minute particles are obtained in the most intimately dispersed form, so that as soon as each of the minute particles of insoluble fungicide is formed it may be attached to the fibers in the stock, prior to actual agglomeration and precipitation of the fungicide particles. Also, the amount of a particular fungicide that is used depends to a substantial extent upon the strength and the like characteristics thereof, that amount which constitutes a fungicidal amount being readily determinable by experiment.

In intimately dispersing the insoluble fungicides in the stock in the beater, certain other conditions have been found to be significant in specific cases. For example, in those cases wherein the insoluble fungicide is precipitated from a sodium salt by the addition of the desired polyvalent metal soluble salt, such as copper sulfate, so as to form the corresponding copper fungicide, the soluble polyvalent metal salt should be added in stoichiometric proportions, so that complete precipitation of all of the fungicidal anionic grouping is accomplished. Also, it is usually preferable to maintain a pH of at least 4.5 in the stock during and after the intimate dispersion of the insoluble fungicide, since lower pHs tend to produce conditions which may free the anionic fungicidal grouping. This is particularly so in the case of the preferred pentachlorophenates employed in the instant invention, and it is usually preferable to maintain a pH of at least 5.5 in the stock when using a pentachlorophenate fungicide.

A substantive agent is by definition one which is capable of attaching itself to the surface of the material to be treated (in this case, the fibers) when such material wherein x is an integer from 2 to 4, which include succinonitrile, glutaronitrile and adiponitrile. For example, if 1 dry fiber weight percent of copper pentachlorophenate and 2 dry fiber weight percent of succinonitrile are added at the beater in the manner hereinbefore described, about 13 percent of the copper pentachlorophenate is retained on the final paper product; and if the succinonitrile is omitted, only 2 percent of the copper pentachlorophenate is retained. Substantially the same results are obtained using the other nitriles in place of succinonitrile.

The acylated polyalkylene amides which I prefer to use are those having 2 to 4 high molecular weight acyl radicals therein, and having 2 to 3 N-alkylene groups therein, such as tetranaphthenoyl triethylenetetramide, hereinafter referred to as TNTT, which is the most preferred substantive agent for use in this invention. Such polyalkylene amides will thus have the formula:

wherein at is an integer from 1 to 2, X is H or a high molecular weight acyl group and R is an alkylene radical. TNTT has the formula:

H-N-CHzOH2(NCHzOH2)2N-H I X! I i! wherein X is the naphthenoyl group. For example, it 0.5 dry fiber weight percent of copper pentachlorophenate and 4 dry fiber weight percent of TNTT are added at the heater in the manner hereinbefore described, about 21% of the copper pentachlorophenate is retained on the final paper product. Pure cultures of Chaetomium globosum, Aspergillus niger, and/ or Aspergillus terreus have shown no growth during twenty-one days incubation in contact with the instant paper product, although all three of such organism will grow under similar conditions if the TNTT is omitted from the beater.

A detailed exemplary procedure is, as follows:

A charge of four pounds of TNTT solids, in the form of siXteen pounds of a 25% solids emulsion thereof, is added to 2,000 pounds of stock in the beater, and thoroughly admixed therewith by heating for 510 minutes. Caustic soda ash is then added to adjust the pH to 10. Next, a charge of ten pounds of sodium pentachlorophenate is added to the beater and circulated therein to completely admix and dissolve the same. The pH is then reduced to 8 by the addition of hydrochloric acid, and a charge of four pounds of copper sulfate is added, in the form of an aqueous solution thereof. After the copper pentachlorophenate has precipitated as a result of this last addition, rosin size and alum can be added in the usual manner, if desired. Preferably, the final pH in the beater should not be below 5.5, since there is a tendency to free pentachlorophenol from the copper pentachlorophenate at lower pHs.

Although the instant invention is particularly advantageous in that it afiords a method of obtaining adequate retention of certain fungicides on unsized as well as sized papers, I have found that the fungicide retention on sized paper made according to my invention is unusually good. On unsized paper, the substantive agents hereinbefore mentioned must be used in order to obtain suitable fungicide retention, but on sized papers the rosin size functions so as to obtain very good retention in the absence of the substantive agent, although the use of the latter in combination with the rosin siZe produces even better results in most cases. For example, it 0.5 dry fiber weight percent of copper pentachlorophenate, 4 dry fiber weight percent of TNTT and 5 dry fiber weight percent of rosin size are added at the heater, in the manner hereinbefore described, about 69% of the copper pentachlorophenate is retained on the final paper product; whereas, if the TNTT is omitted, about 55% of the copper pentachlorophenate is retained. Substantially the same results may be obtained using others of the fungicides hereinbefore mentioned.

Also, comparable effectiveness of rosin size alone and rosin size plus the water soluble nitrile substantive agents may be shown from the following results showing (in the left hand column) the proportions, on a dry fiber weight percent basis, of ingredients used in several charges added to the beater, and showing (in the right hand column) the percent of the copper pentachlorophenate fungicide retained on the final paper product in each case:

Charge: Retention, percent 1% Fungicide 2 1% Fungicide, 2% succinonitrile 13 1% Fungicide, 2% rosin size 36 1% Fungicide, 2% rosin size, 2% succinonitrile. 38 1% Fungicide, 2% rosin size, 4% succinonitrile 38 1% Fungicide, 2% rosin size, 2% adiponitrile 36 It will, of course, be understood that various details of compositions and operations may be varied through a wide range without departing from the principles of this invention and it is, therefore not the purpose to limit the patent granted thereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. A method of preparing m-oldproof paper that comprises the steps of dissolving in paper stock in the beater sodium pentachlorophenate and 0.01 to 5 dry fiber weight percent of a substantive agent selected from the class consisting of tetranaphthenoyl tetraethylene tetramide and compounds having the formula:

NC(CH2 xCN wherein x is an integer from 2 to 4, precipitating copper pentachlorophenate in situ by the addition of copper sulfate, the amounts employed being such that the stoichiometric equivalent of copper sulfate is used to react with the sodium pentachlorophenate to obtain 0.01 to 5 dry fiber weight percent of copper pentachlorophenate, and then intimately dispersing in the stock rosin size and the requisite alum for reducing the stock to an acid pH of at least 4.5.

2. A mold proof fibrous paper web having a rosin size and having afiixed to the fibers 0.01 to 5 dry fiber weight percent of a substantive agent selected from the class consisting of tetranaphthenoyl tetraethylene tetramide and compounds having the formula:

wherein x is an integer from 2 to 4, and as a fungicide, 0.01 to 5 dry fiber weight percent of copper pentachlorophenate afiixed to the fibers by precipitation upon the fibers prior to web formation.

References Cited in the file of this patent UNITED STATES PATENTS 2,067,047 Ellis (1) Jan. 5, 1937 2,144,271 Quinn Jan. 17, 1939 2,161,654 Ellis (2) June 6, 1939 2,365,833 Morrill et al Dec. 26, 1944 2,487,899 Sherman Nov. 15, 1949 2,577,041 Seymour Dec. 4, 1951 2,601,598 Daniel et a1 June 24, 1952 FOREIGN PATENTS 3,004 Great Britain 1890 

1. A METHOD OF PREPARING MOLDPROOF PAPER THAT COMPRISES THE STEPS OF DISSOLVING IN PAPER STOCK IN THE BEATER SODIUM PENTACHLOROPHENATE AND 0.01 TO 5 DRY FIBER WEIGHT PERCENT OF A SUBSTANTIVE AGENT SELECTED FROM THE CLASS CONSISTING OF TETRANAPHTHENOYL TETRATHYLENE TETRAMIDE AND COMPOUNDS HAVING THE FORMULA 